1. Field
The present invention relates to a surface position detecting apparatus, exposure apparatus, surface position detecting method, and device manufacturing method to detect a surface position of a predetermined surface.
2. Description of the Related Art
In an exposure apparatus which transfers a pattern formed on a mask, through a projection optical system onto a photosensitive substrate, it is sometimes the case that the depth of focus of the projection optical system is shallow and that a photosensitive surface (transfer surface) of the photosensitive substrate is uneven. For this reason, the exposure apparatus needs to perform accurate alignment of the photosensitive surface of the photosensitive substrate with an image plane of the projection optical system.
For example, an oblique incidence type autofocus sensor is known as a surface position detecting apparatus which detects a surface position of the photosensitive substrate (surface position of the photosensitive surface) along the optical-axis direction of the projection optical system (cf. Japanese Patent Application Laid-open No. 4-215015). This oblique incidence type autofocus sensor is configured to project an image of a slit from an oblique direction to the photosensitive substrate as a predetermined surface, detect position information of the image of the slit formed by light reflected on the predetermined surface, and detect the surface position of the photosensitive substrate, based on the position information.